docs: def _get_table(name):
    """ Given a variable or table name, get a Table if it exists.
  
    Args:
      name: the name of the Table or a variable referencing the Table.
    Returns:
      The Table, if found.
    """
    # If name is a variable referencing a table, use that.
    item = google.datalab.utils.commands.get_notebook_item(name)
    if isinstance(item, bigquery.Table):
      return item
    # Else treat this as a BQ table name and return the (cached) table if it exists.
    try:
      return _existing_table_cache[name]
    except KeyError:
      table = bigquery.Table(name)
      if table.exists():
        _existing_table_cache[name] = table
        return table
    return None